Add "physics" MathJax package

[pnb]

Needed for papers like 4MSop43m4O (manually added).

E.g.:

MathJax = {
    loader: {
        load: ['[tex]/textmacros', '[tex]/physics']
    },
    tex: {
        tags: 'ams',
        macros: {
            bm: ["\\boldsymbol{#1}", 1],
            textsc: ['\\style{font-variant-caps: small-caps}{\\text{#1}}', 1],
            relax: '',
            mathds: ["{\\mathbb \#1}", 1],
            mathbbm: ["{\\mathbb \#1}", 1]
        },
        packages: {'[+]': ['textmacros', 'physics']}
    }
}